Epitaxial growth of BaZrO₃ films on single crystal oxide substrates using sol-gel alkoxide precursors

Epitaxial BaZrO₃ (barium zirconium oxide) films were grown on single crystal substrates. A BaZrO₃ precursor solution was prepared by sol-gel synthesis using an all-alkoxide route. The barium precursors were prepared by reacting barium metal with 2-methoxyethanol, and zirconium precursors were prepared by exchanging ligands between zirconium n-propoxide and 2-methoxyethanol. The resulting BaZrO₃ precursor solution was partially hydrolyzed and spin-coated on sapphire (100), SrTiO₃ (strontium titanium oxide) (100), and LaAlO₃ (lanthanum aluminum oxide) (100) substrates. The films were post-annealed in oxygen at 800°C for 2 min in a rapid thermal annealer. The coating and the annealing procedures were repeated three times to obtain the desired thickness, 300 nm. X-ray diffraction studies showed the presence of a single (100) cube texture for BaZrO₃ films on SrTiO₃ and LaAlO₃ substrates. The BaZrO₃ films grown on sapphire had a random texture. The BaZrO₃ films grown on SrTiO₃ substrates had a sharp texture compared to that on LaAlO₃ substrates. This may be due to the relatively smaller lattice mismatch between SrTiO₃ and BaZrO₃.